recordcutting (13)

The Reliable Stylus Heating System: Type 192

The Agnew Analog Reference Instrument Type 192 is a minimalist, industrial-grade stylus heater supply unit, designed and built to last forever.
It is a current-regulated design, set at the factory for 550 mA, in an ultra-ruggedized configuration, for maximum reliability in constant-duty environments, when downtime is not an option.

Direct-Drive Conversion on a Fairchild Lathe

The Fairchild line of disk recording lathes, first appearing in the early 1930’s, featured a General Electric hysteresis synchronous AC motor, running at high speed, with a worm and gear reduction to drive the platter. While this system in its various permutations in their different models was impressively well made and performed well for its time (see here for a more detailed description and pictures), a direct-drive system with a floor mounted motor is clearly the way to go if the highest level of performance is to be attained.

Type 1501 Stylus Shank Adapter gets a Flat!

Our popular Agnew Analog Reference Instrument Type 1501 Stylus shank adapter was intended to make it possible to use the Neumann-style taper shank stylus (Transco 320, Adamant NSH-2, etc) with vintage mono heads such as the Presto 1-C and 1-D, which need a long shank stylus.

Up to now, customers would just install the adapter and leave it there, only occasionally replacing the stylus. One customer, however, wanted to be able to leave the stylii aligned in the adapter, and change them out without needing to realign.

Fitting a Neumann Cutter Head to a Presto Lathe

Neumann cutter heads have a rib along the back, for mounting. Presto lathes, on the other hand, together with the vast majority of non-Neumann vintage lathes (Rek-O-Kut, Fairchild, etc.), have a mount with two slots, for cutter heads with two threaded holes on the back (Audax, Presto, Fairchild, RCA, etc).

Rek-O-Kut Master Pro System with modified Presto 1D Cutter Head

Tasos of Epos Laboratory (a Grado retipping specialist) from the beautiful south of Greece is the lucky owner of this 1950's Rek-O-Kut disk recording system.

It consists of a Rek-O-Kut Model V 16" turntable, which he found in the USA (where else?) as a non-runner. The motor was in bad shape and refused to run at all. Even if it would run, it was expecting to be fed on a regular diet of 110 VAC/60 Hz!

Presto 75A Restoration Project

A customer recently imported a vintage Presto 75A disk recording lathe from the USA, with a view to cutting records in Europe.

He quickly discovered, like many people before him, that it was spinning a bit slower than it should, when operated from 50 Hz mains, via a simple step-down transformer. As with most vintage record cutting machines, the platter is powered by a synchronous AC motor, which "locks" to the line frequency.

Presto 75A: 50 Hz 33 1/3 and 45 rpm Conversion

It would appear that 50 Hz conversions of vintage "made in USA" disk recording lathes are becoming rather fashionable! Last week we examined how we converted a Rek-O-Kut Model V by machining a new capstan and making a special transformer, Type 1760.

We have done 50 Hz conversions (and even some 60 Hz ones!) on many different lathes and turntables, using all of the possible methods of doing so: New rubber rollers, new capstans, new belt pulleys and even electronic frequency conversion (Agnew Analog Type 191 frequency converter) for professional disk mastering systems.

This week, we will have a look at the Presto 75A, a high quality machine, dating from the 1930's, which was even used by the BBC as a broadcasting turntable!

Presto MRC-16 Variable Pitch Modification

A rather optimistic gentleman arrived with a Presto MRC-16 disk recording lathe, inquiring about the possibility of repairing the broken suspension and making a cutter head bracket from scratch. He then asked about the possibility of figuring out some way in which lead-in, lead-out, and track mark spirals could be cut on this machine, which was originally intended as a very basic machine, with no provision for spirals, not even a hand crank. Then came the really ambitious part: He would ideally like to be able to adjust the pitch and if possible, control the lathe through his computer!

One glance at the steampunk aesthetic of the manufacturer's name plate and the overall state of this primitive machine would have been enough to deter the average engineer, in fear that there might be something potentially radioactive hiding within...

Motional Feedback Disk Recording System Design


In 2015, J. I. Agnew started developing a high-end cutting amplifier for disk mastering systems, to be used with motional feedback stereophonic cutter heads. During this process, he investigated the design and implementation problems of such transducers in great detail. As usual, he documented his progress, which evolved into an engineering report, titled "An Investigation of Motional Feedback Disk Recording System Design", which was accepted for publication in the November 2018 issue of the Journal of the Audio Engineering Society, following the customary peer review process.

Lab Report: The Agnew Analog Stereophonic Cutter Head

Happy new year! Time to reveal what has been secretly developing in the lab throughout the past year: A stereophonic cutter head of an entirely unique design, invented by J. I. Agnew during his work with experimental transducers for measurement and testing purposes.